1. Field of the Invention
The present invention relates to a providing apparatus and a providing method that provide information required for a secure communication between a first device and a second device to the first and second devices, a communication device and a communication method that receive information required to ensure secure communication with the communication partner from the providing apparatus, and a program for realizing the providing method or the communication method.
2. Description of the Related Art
Security architecture for Internet protocol (IPsec) is a standardized protocol having enough functions and safety to ensure the security in a general Internet protocol (IP) layer. The core of the IPsec is automatic generation of a security association (SA) conforming to an Internet key exchange (IKE) protocol defined in RFC2409 “The Internet key exchange (IKE)”. The SA is established in two phases: Phase1 (or Internet security association and key management protocol (ISAKMP) SA) and Phase2 (or IPsec SA). The IPsec is disclosed in, for example, U.S. 2001042201.
In the Phase1 in an aggressive mode, an encryption algorithm for an IKE communication channel is selected in the first round-trip, key (key for IKE communication) exchange is performed in a Diffie-Hellman (DH) key exchange algorithm in the second round-trip, and the communication partner is authenticated in the third round-trip. In the Phase2, encryption algorithms or secret keys used in the encapsulating security payload (ESP) or the authentication header (AH) of a security protocol are exchanged using a secret communication channel, established in Phase1, in the first round-trip to transmit the subsequent connection acknowledgement only as transmission. The setting information exchanged in the above manner is registered as SA entries in security association databases (SAD) of the corresponding terminal devices and is utilized in secure communications between the terminal devices.
The IPsec communication is standardized so as to be automatically set between the corresponding terminal devices. However, some pre-settings are required.
Authentication by a pre-shared key method is generally supported as the authentication performed in the third round-trip in Phase1. In the pre-shared key method, it is presumed that a shared key, which is effective only between the two terminal devices performing the secure communication, is directly set for the corresponding devices by a skilled manager. Accordingly, although the pre-shared key method is operational between a few specified devices, it is difficult to operate the pre-shared key method between an unspecified number of devices.
For example, the DH key exchange algorithm and a public key encryption algorithm used in the IPsec are complicated and it takes a few seconds or more to process the IPsec in a mobile terminal or the like, which has a relatively little CPU power. Hence, in devices with relatively little CPU power, it is necessary to use a dedicated arithmetic chip, which creates implementation problems.